1. Field of the Invention
The present invention relates in general to ceramic packages and more particularly to a ceramic IC (integrated circuit) package base or main body constructed of a ceramic substrate and a circuit wiring, resistor wiring, condenser, etc. formed inside and/or outside the ceramic substrate, which makes it easier to carry out a check or inspection for its insulation defect, short circuit defect, etc.
2. Disclosure Information
Generally, a ceramic package main body equipped with an integrated circuit, etc., is produced by printing a circuit wiring pattern made of a tungsten paste or the like onto a ceramic green sheet or filling through holes of a ceramic green sheet with the paste, laminating a plurality of ceramic green sheets with the circuit wiring pattern and the through holes and forming the laminated sheets into a predetermined shape, and then co-firing the laminated sheets.
Recently, in order to meet with a requirement for a high density integrated circuit and a small-sized IC package, the circuit wires formed inside and outside of the package main body increase in number whilst becoming finer and more complicated in shape, so that the distance between the adjacent circuit wires is becoming smaller.
Accordingly, even a small shift of the printed wires or the like error in size or arrangement of same during printing of paste and/or forming of the package main body may cause a short across the adjacent wires.
In order to change the characteristics of the circuit wiring such as a resistance, a particular portion of a particular wire is formed into a fine width wire or formed of a particular resistance paste containing an increased amount of ceramic component.
In such a case, the wire is liable to be cut off so that a disconnection or open defect may possibly be occur or the resistance value may not be within a desired range.
Usually, a circuit wiring is designed elaborately so as not to cause such a defect. However, because of the shape, etc. of the circuit wiring it is obliged to be designed so as to have a portion liable to cause a defect of the above described kind, resulting in occurrence of a defect of the above described kind concentrated at a particular portion of the circuit wiring.
Further, in order to meet with an increase in operation frequency of a recent integrated circuit, there occurs increasingly such a case in which a condenser is built in a package main body in order to prevent malfunction caused by noise.
In order to form such a condenser, various methods have been proposed. One of the methods is to form a condenser inside the package main body and another is to form a condenser on the surface of the package main body by the use of a thick-film and/or thin-film forming technique.
Particularly, in case a ceramic material similar to that forming the ceramic substrate or capable of being co-fired with the same is used for forming a dielectric layer inside a package main body, the dielectric layer is often made thinner with a view to making the electrostatic capacity larger since the dielectric constant of the ceramic material is low. In this instance, an insulation defect or short-circuit defect between electrodes forming a condenser will be often caused or there may possibly occur such a case where a desired electrostatic capacity is not attained.
In the meantime, end portions of the above described circuit wiring are formed with terminals for connection with an integrated circuit or the like, such as bonding pads or bumps. That is, by wire bonding or tape-automated bonding (TAB), the bonding pads are connected to an integrated circuit, or by flip-chip solder bonding, also called controlled-collapse-chip-connection (C4) the bumps are connected to an integrated circuit.
Other end portions of the circuit wiring are generally affixed with pins, leads, solder balls, or the like to serve as external terminals for connection with other circuit components.
Further, electrodes forming a condenser are connected to the circuit wiring.
In order to improve the bondability, the resistance to oxidation, etc., it has been widely practiced to plate the bonding pads, bumps, external terminals, or the like with a precious metal, particularly gold, even when they are plated with nickel as a base metal.
In this instance, although there are some cases where electroless plating is employed for this end, electroplating is used in many cases for the reason of the quality of coating, easy process, easy control of plating solutions, etc.
The electroplating requires to set up a potential at a portion to be plated. There are some methods available to this end, that is, one wherein plating contacts are brought into direct contact with bonding pads, or the like to make them conduct, and one wherein a plurality of external terminals are preformed in such a manner as to constitute a single unit and fixed to the end portions of the circuit wiring so that all of the external terminals are made to conduct and after plating the external terminals are separated one by one.
However, those methods are encountered by a problem in that the external terminals are partially not plated, and the process for separating the terminals one by one is troublesome, etc.
For the above reasons, the following method is employed in many cases.
That is, as shown in FIG. 8, connection wires 26 which are so called plating tie bars are previously printed together with circuit wires 22 onto a ceramic green sheet in such a manner as to extend to the peripheral side surfaces 21A.about.21D of the green sheet. The ceramic green sheet and another ceramic green sheet or sheets produced similarly as above are laminated and cut into a predetermined shape. Then, a conductive paste is printed onto the peripheral side surfaces 21A.about.21D so as to form-conductive layers 27A.about.27D through which the connection wires 26 are electrically connected to each other. Under this condition, the laminated ceramic green sheets are fired to complete a ceramic substrate 21. Further, desired external terminals (not shown) are affixed to the ceramic substrate 21. Thereafter, the conductive layers 27A.about.27D are brought into contact with plating contacts for plating the pads, bumps, terminals and the like all at once. After that, the conductive layers 27A.about.27D are removed by grinding or the like for thereby making the circuit wires 22 be independent from each other, whereby the package main body is completed.
In such a case, the above described conductive layers 27A.about.27D, as shown in FIG. 8, are formed on the peripheral side surfaces 21A.about.21D in such a manner as to be conductive to each other by way of connection wires 26a.about.26h. In another method, the conductive layers 27A.about.27D may be formed so as to be connected to each other by being extended around the corners of the ceramic substrate 21.
By the above manner, if only one of the conductive layers 27A.about.27D is brought into contact with the plating contacts and electrically connected thereto, it becomes possible to plate all of the pads, terminals, and the like at once, thus being convenient since the plating can be attained with ease and assuredness.
However, in case of such a process being employed, the inspection or check of the package main body for the above described defect of the circuit wires 22 requires to carry out inspections of the circuit wires independently, so that it becomes possible to carry out the inspection only after the plating of the ceramic substrate 21 and removal of the conductive layers 27A.about.27D.
In such a case, it is obliged to throw away a defective package main body in a state of being added with value such as gold plating, etc., thus increasing the manufacturing cost. This is particularly true when the yield rate in production of the package main body is low due to the difficulty in design of the circuit wiring and/or the necessity of being provided with a condenser or the like, which leads to a further problem on a manufacturing process that it becomes necessary to add good products to the manufacturing line hastily in order to compensate for the defective products.